Many polymers have the unpleasant property of losing their color upon exposure to light. Such polymers include polyphenylene ethers, aromatic polyesters such as polybutylene terephthalate, polyethylene terephthalate and styrene-containing (co)polymers, for example, polystyrene, rubber-modified "high-impact" polystyrene, styrene-acrylonitrile (SAN) copolymers, acrylonitrile-butadiene-styrene (ABS) polymers, especially such styrene-containing (co)polymers which have been made self-extinguishing by the addition of aromatic bromine compounds, as well as polymer mixtures comprising one or more of the said polymers.
The present invention relates to a polymer mixture which comprises a polyphenylene ether polymer, optionally a styrene polymer and one or more dyes. Such mixtures and their mode of preparation are to be found in numerous patent publications, for example, the U.S. Pat. Nos. 3,306,874; 3,306,875; 3,257,357; and 3,257,358. The use of styrene polymers in such mixtures is described more in particular in the U.S. Pat. Nos. 3,383,435 and 3,663,661.
These mixtures can be colored by incorporating dyes therein. Generally, when articles formed from these mixtures are exposed to light, discoloring occurs. This discoloring is probably associated with a yellowing of the polyphenylene ether polymer used. The present invention provides a solution to this problem.